Laser-induced ultrasound imaging of multi metal laminate with complex interface

Abstract

The corrugated rolling process is a new type of metal clad plate production method, and the high-precision testing of the corrugated interface is of great significance to the improvement of product quality. This paper integrates laser ultrasonics and Synthetic Aperture Focusing Technique (SAFT) to characterize the corrugated interface accurately. A photoacoustic platform is developed for the non-contact automatic acquisition of laser ultrasonic signals, and these signals are filtered and gated to achieve high-quality imaging. Meanwhile the effect of signal acquisition efficiency on imaging quality is also discussed. Since the ultrasonic excitation point is separated from the detection point in this experiment, an interface profile calculation method based on the ellipses’ common tangent line is developed, and the double-layer imaging of the corrugated clad plate is realized using the fitting curve of the interface profile and Fermat’s principle. The results show that the image obtained by this method are consistent with the results obtained by the 3D surface profiler and Energy Dispersive Spectroscopy (EDS), which indicates that this method can not only provides an essential reference for the research of corrugated rolling process, but also provides new approaches for non-contact non-destructive-testing applications in the materials processing industry.